[FIR2IR] Fix generation of val initialization after smart-cast, again

#KT-57284

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/generators/CallAndReferenceGenerator.kt

@@ -572,7 +572,7 @@ class CallAndReferenceGenerator(
                         // If we found neither a setter nor a backing field, check if we have an override (possibly fake) of a val with
                         // backing field. This can happen in a class initializer where `this` was smart-casted. See KT-57105.
                         if (setter == null && backingField == null) {
-                            backingField = irProperty.overriddenSymbols.firstNotNullOfOrNull { it.owner.backingField }
+                            backingField = irProperty.overriddenBackingFieldOrNull()
                         }
 
                         when {
@@ -624,6 +624,13 @@ class CallAndReferenceGenerator(
         }
     }
 
+    private fun IrProperty.overriddenBackingFieldOrNull(): IrField? {
+        return overriddenSymbols.firstNotNullOfOrNull {
+            val owner = it.owner
+            owner.backingField ?: owner.overriddenBackingFieldOrNull()
+        }
+    }
+
     fun convertToIrConstructorCall(annotation: FirAnnotation): IrExpression {
         val coneType = annotation.annotationTypeRef.coneTypeSafe<ConeLookupTagBasedType>()
             ?.fullyExpandedType(session) as? ConeLookupTagBasedType

compiler/testData/codegen/box/smartCasts/propertyInitializationAfterSmartCast.kt

@@ -7,10 +7,23 @@ open class MessageBusImpl {
 
     init {
         this as RootBus
-        parentBus = "OK"
+        parentBus = "O"
+    }
+}
+
+class RootBus2: CompositeMessageBus2()
+
+open class CompositeMessageBus2: MessageBusImpl2()
+
+open class MessageBusImpl2 {
+    val parentBus: Any?
+
+    init {
+        this as RootBus2
+        parentBus = "K"
     }
 }
 
 fun box(): String {
-    return RootBus().parentBus as String
+    return "" + RootBus().parentBus + RootBus2().parentBus
 }